Various mechanisms can be provided to allow a user to access and operate a vehicle. For example, where the vehicle is a multi-user vehicle, e.g., a vehicle to which a particular user may be provided temporary or one-time access, the user could be provided with a physical key, an electronic fob, etc., to allow the user to access and operate the vehicle. An authorized user might also be provided with means for electronic authentication, e.g., a password or PIN (personal identification number) that could be input via an interface provided on the vehicle. However, electronic authentication information (password, PIN, etc.) can be stolen or guessed, possibly allowing an unauthorized user to actuate vehicle functions, or may be lost or forgotten, preventing an authorized user from actuating vehicle functions.